Well known fluid flowmeters use paired rotors on parallel shafts within intersecting cylindrical chambers. Fluid flows into the chamber, turns the rotors, and exits the chamber. The number of turns of the rotors is measured to indicate the amount of fluid flow. Perhaps the best known types of flowmeters with paired rotors are water meters.
One problem generally associated with the meters is the accuracy in reading. Often readings are taken by extending shafts, on which the rotors are mounted, through the walls of the chambers and the mounting gears on the extended shafts to turn meters. In many cases that is satisfactory.
In meters which require high accuracy the extended shafts may not be useful, and other forms of measuring become important. Some forms of measurement have used sensors on the outside of a chamber to sense movement of lobes within the chamber. Some of those forms use magnets embedded in the lobes within the chamber and sensors outside of the chamber to sense the passage of magnets. Other devices have used magnetic couplings between shafts turning on bearings within the chamber and shafts outside of the chamber.
Difficulty in magnetic coupling and in conforming indicator load to available torque produced by the rotors within the chamber has produced varied success. The problem is intensified when using the meters with fluids which are inimicable to the use of bearings, viscous fluids, varied fluids or fluids which require periodic cleaning of the meters.
An example of such a fluid is automotive paint.
In the course of painting automobiles it is important to precisely control the amount of paint being applied to the automobile and to coordinate the amount of paint being applied with the relationship of the applicators to the automobile body.
Paint lines and meters must be periodically cleaned with solvents having viscosities greatly differing from the paint. While it is not necessary to precisely measure the solvents, it is extremely important that all of the paint be taken from the meter and all of the solvents be removed from the meter. Consequently, it is highly desirable to use meters without bearings and ones which are easily and effectively cleaned.
The present invention is directed to the provision of such meters with highly accurate internal flow characteristics and highly accurate external measuring systems.